The synovial layer covering the inside of diarthrodial joints forms the main focus of the chronic inflammatory response during rheumatoid arthritis (RA) and is the major producer of pro-inflammatory cytokines and enzymes which cause irreversible cartilage and bone destruction (Klippel, 1997) within this disease. The key cells in the RA synovium mediating tissue damage are thought to be macrophages (Kinne et al., 2000) and synoviocytes (Pap et al., 2000), but also T cell responses may drive part of the synovial inflammation and destruction (Firestein and Zvaifler, 2002).
Rheumatoid arthritis is a chronic inflammatory arthritis that afflicts approximately 1% of adults (Mitchell, 1985). It affects the synovial membrane and leads to irreversible damage of cartilage and bone. The distribution of affected joints is symmetric and typically involves the small articulations of the hands and feet, although the larger appendicular joints like the shoulders and hips are often affected in established disease. Joint deformities, including ulnar deviation of the metacarpal phalangeal joints of the hand or destruction of the weight bearing joints, can occur late in the disease.
The symptoms of the disease result from a massive increase in the number of cells lining the synovium of the joint. The various cell types that are present include type A synoviocytes, which have the characteristics of monocytes or terminally differentiated macrophages, and type B synoviocytes, which are fibroblast-like. As these cells increase in number, the continuous inflammation causes initial symptoms. Eventually, local release of enzymes by the synovial internal lining degrades the extracellular matrix and causes deformity. The mainstays of therapy for rheumatoid arthritis include non-steroidal anti-inflammatory drugs, injectable gold salts, immunosuppressive agents, and methotrexate. While controlled studies do show some clinical benefit from these drugs, improvement is often limited and toxicity is common. Furthermore, most data suggest that these agents do not halt the rate of cartilage or bone destruction. Hence, a novel treatment that is directed at the pathogenesis of the disease with potential disease modifying activity would be a major improvement. The origin of the cells in the hyperplastic synovial lining in chronic inflammatory joint diseases remains controversial. Necrosis and apoptosis are two basic processes by which cells may die. In necrosis cell death usually is a result of cell injury. The cells tend to swell and lyse, and the cell contents ultimately spill into the extracellular space. By contrast, apoptosis is a mode of cell death in which single cells are deleted in the midst of living tissues. Apoptosis accounts for most of the programmed cell death (PCD) in tissue remodeling and for the cell loss that accompanies atrophy of adult tissues following withdrawal of endocrine and other growth stimuli. In addition, apoptosis is believed to be responsible for the physiologic death of cells in the course of normal tissue turnover (i.e., tissue homeostasis) (Kerr et al., 1972; Wyllie et al., 1980).
The most abundant cell type present in RA synovium is the macrophage. The majority of synovial macrophages are thought to arise from monocytes which infiltrate into the synovium where they mature into tissue macrophages and dendritic cells (DC) under influence of growth factors like GM-CSF and IL-4 (Jonuleit et al., 1996). Synovial macrophages become activated by as yet unknown factors.
Macrophage antigens/lectins play an important role in the recognition and destruction of foreign and diseased cells. The selective modulation of the expression and specificity of a novel human macrophage antigen may allow the successful management of diseases related to macrophage function.
Macrophages are bone marrow-derived cells that form an important part of the host defense system. They play a role in physiological as well as pathological processes, such as inflammation, fibrosis atherogenesis, and tumor invasion.
Macrophages are relatively large (10-20 μm), long-lived, amoeboid, phagocytic and pinocytotic cells present in blood, lymph and other tissues. They are derived from monocytes which form a pool of precursors migrating from blood into peripheral tissues such as liver, spleen, lung, lymph nodes, peritoneum, skin, brain and bone, where they differentiate into macrophages with organ specific features. Macrophages play important roles in host resistance to a variety of pathogenic microorganisms, having important functions in, for example, phagocytosis, inflammation, antibody formation, cell-mediated cytotoxicity and delayed hypersensitivity.
In this regard, the major characteristic of macrophages is their ability to recognize, internalize and destroy a variety of foreign and endogenous substances and, thus, to function as scavengers that engulf pathogenic organisms, such as bacteria, parasites and viruses. Macrophages also remove extravasated blood cells or dead cells in tissues and, thereby, participate in the maintenance of tissues. Furthermore, macrophages are thought to play a role in immune response by presenting foreign antigens (i.e., are antigen-presenting cells) to lymphocytes. The macrophages have been shown to be able to bind “nonself” pathogens directly, or they recognize pathogens as foreign because they have been coated by antibodies or complement. The exact recognition mechanism is unknown, but it has been proposed that receptors with broad binding specificity are used to discriminate between self and nonself.
Activated synovial macrophages are the main producers of IL-1 (van den Berg and van Lent, 1996) and TNFα (Feldmann et al., 1996). Recent studies suggest that interfering with the function of these cytokines is an effective approach for therapy in human RA (Feldmann et al., 1996; Bresnihan et al., 1998). Furthermore, cartilage and bone degrading enzymes like matrix metalloproteinases (MMPs) and serine proteinases are also produced (Katrib et al., 2001) by macrophages and the amount of these cells in the synovium appeared to be strongly correlated to severity of the cartilage destruction (Mulherin et al., 1996; Yanni et al., 1994).
Apart from macrophages, T cells extensively infiltrate the RA synovium. Although a plethora of antigens have been suggested as a possible cause of this disease, the relationship between T cell reactivity and pathogenesis remains obscure. Most T cells lack the morphology, surface phenotype and cytokine secretion profile of T cell blasts (Fox, 1997). Furthermore levels of IL-2 in the synovium are low (Firestein and Zvaifler, 1990) and only a small minority of synovial T cells express IL-2Rs (Fox et al., 1990) which suggests that the number of active T cells is low within the synovium. In contrast, naive (CD45RA) and memory (CD45RO) resting T cells are extensively found within RA synovium (Summers et al., 1994) but their presence is thought to be an epiphenomenon. In vitro studies have shown that interaction between resting T cells and monocytes (Dayer and Burger, 1994) or fibroblasts (Chizzolini et al., 2000) may be involved in cell activation and elevated release of cytokines and enzymes. Which surface receptors are important in the synovial naive T cell-macrophage interaction remains to be discovered.
Naive T cells are characterized by a high expression of ICAM-3 which is a member of the IgG supergene family and is rapidly downregulated after activation (Vazeux et al., 1992). Recently a novel ICAM-3 binding C-type lectin, known as DC-SIGN, expressed by dendritic cells in tissues of healthy donors was found. It was observed that DC-SIGN mediates adhesion between dendritic cells and ICAM-3 on naive T cells and appears to be essential for DC-induced T cell proliferation (Geijtenbeek et al., 2000; Steinman, 2000).
WO 00/63251 describes DC-SIGN, which binds ICAM receptors on the surface of T cells. Modulation of immune responses can be achieved by affecting the interaction between dendritic cells and T cells. Immune responses can be inhibited or prevented by preventing the interaction of DC-SIGN on dendritic cells with receptors on T cells, e.g., by using antibodies specific for DC-SIGN. Alternatively, an immune response to an antigen can be potentiated by binding the antigen to DC-SIGN on dendritic cells such that the antigen plus DC-SIGN is taken up by dendritic cells and processed and presented to T cells. The contents of WO 00/63251 are specifically incorporated herein by reference in their entirety.
WO 96/23882 describes a murine and human receptor with C-type lectin domains that is abundantly expressed on the surface of dendritic cells and thymic epithelial cells. The murine receptor—named “DEC-205”—is described as a 205 kDa protein with an isoelectric point of about 7.5 that contains 10 C-type lectin domains and that is homologous to the macrophage mannose receptor (MMR).
WO 96/23882 further describes monoclonal and polyclonal antibodies against DEC-205. However, these antibodies were not able to block dendritic cell function. In particular, monoclonal and polyclonal anti-DEC-205 antibodies were unable to inhibit the interaction between dendritic cells and helper T cells, both in vitro (as determined by the inability of anti-DEC-205 to inhibit allogenic T cell proliferation in a one way mixed leukocyte reaction) and in vivo (as determined by the inability of anti-DEC-205 to inhibit an in vivo response, i.e. in a local graft-versus-host (GVH) reaction). These results suggest that the DEC-205 receptor is not involved in dendritic cell-T-cell interaction (i.e. adhesion) and that the anti-DEC-205 antibodies cannot be used to modulate the immune response.
Curtis et al. (1992), as well as in WO 93/01820, describe a non-CD4 gp120 receptor isolated and cloned from human placenta tissue. This gp120 receptor is expressed on mammalian cells which do not exhibit high levels of CD4, such as placenta, skeleton muscle, brain, neural and mucosal cells, as well as other tissues and cells including colon, thymus, heart, T cells, B cells and macrophages (but not in the liver or the kidney). The amino acid sequence of the C-type lectin gp120 receptor disclosed in SEQ ID NOs:1 and 2 of WO 93/01820 has a high degree of sequence homology (>98%) with the C-type lectins that were found to be present on dendritic cells (WO 00/63251; Geijtenbeek et al., 2000).
Curtis et al. (1992) and WO 93/01820 further discuss the role this C-type lectin receptor plays in the infection of the aforementioned cells/tissues with HIV, i.e. by binding the major HIV envelope glycoprotein gp120 prior to internalization of the virion into the cell. It was found that inhibition of the C-type lectin gp120 receptor could reduce or inhibit HIV infection of these cells/tissues. As suitable inhibitors, WO 93/01820 discloses mannose carbohydrates, fucose carbohydrates, plant lectins such as concanavalin A, specific antibiotics such as pradimicin A, and sugars such as N-acetyl-D-glucosamine and galactose (which however are described as less potent). These compounds and compositions containing them are used either in vitro or in vivo to inhibit the binding of HIV to the cell surface.
WO 93/01820 further discloses that binding of HIV to COS-7 cells can be inhibited by pre-incubation of gp120 with an anti-gp120 monoclonal antibody (named “antibody 110.1”). However, this antibody is not directed against the C-type lectins, but against the gp120 protein.
Neither Curtis et al. (1992) nor WO 93/01820 mentions or suggests the presence of such a C-type lectin on dendritic cells or on macrophages, nor do these references mention or suggest their role in dendritic cell—T cell interaction during the initial stages of an immune response nor in macrophage—T cell interaction in rheumatoid arthritis.
WO 95/32734 describes FcγRII (CD32) bridging (or crosslinking) compositions and their use in modulating the immune response to specific antigens. This reference is based upon the finding that the bridging of FcγRII (CD32) molecules on antigen presenting cells (APCs) impairs the expression of the essential co-stimulatory molecules B7-1/2 (i.e. prevents their up-regulation) and thereby impairs the expression of (i.e. causes the down-modulation of) the adhesion molecule ICAM-3, with the functional consequence of an impaired capacity of the monocytes to co-stimulate the activation of antigen-specific T cells (i.e. resulting in the modulation of antigen-specific T cell unresponsiveness). The bridging agent is chosen from aggregated human IgG molecules or Fc-fragments thereof; bi- or multivalent monoclonal antibodies to FcγRII or fragments thereof, or a fusion of two or more human IgG Fc parts.
WO 95/32734 is directed towards modulating (i.e. inhibiting) the co-stimulation signal required for T cell activation (i.e. besides the primary signal of TcR/CD3 interaction), in particular to induce proliferation and maturation into effector cells. WO 95/32734 is not directed towards modulating dendritic cell—T cell adhesion or macrophage—T cell adhesion, nor does it disclose or suggest either the presence of C-type lectins on the surface of dendritic cells or macrophages in persons with rheumatoid arthritis or their interaction with the ICAM-3 receptors on T cells.
WO 98/02456 discloses a group II human C-type lectin isolated from a stimulated human macrophage library. WO 98/49306 discloses a group IV C-type lectin present in human pancreatitis-associated protein (“PAP”). WO 98/41633 discloses a group V human C-type lectin isolated from a human tumor clone.
WO 98/02456, WO 98/49306 and WO 98/41633 further disclose methods for producing antibodies against these C-type lectins. However, none of these references relates to C-type lectins on macrophages in persons with rheumatoid arthritis.
Dendritic cells (DC) are professional antigen-presenting cells that capture antigens in the peripheral tissues and migrate via lymph or blood to the T cell area of draining lymph nodes and spleen. Here they present processed antigens to naive T cells, initiating antigen-specific primary T cell responses.
DC are unique in their ability to interact with and activate resting T cells. However, prior to publication of WO 00/63251 and Geijtenbeek et al. (2000), it was largely unknown how DC-T cell contact is initiated and regulated. Therein, the role of ICAM-3 in DC-T cell interactions was investigated. It was demonstrated that although DC strongly adhere to ICAM-3, this adhesion is not mediated by LFA-1, αD or any other integrin. In the search for this novel ICAM-3 receptor on DC a C-type lectin receptor was cloned, designated DC-SIGN, which is preferentially expressed by DC. Besides its prominent role in DC-T cell clustering and initiation of T cell responses, it was discovered that DC-SIGN is a major HIV-1 receptor involved in infection of DC and subsequent HIV-1 transmission to T cells. Thus HIV-1 and resting T cells exploit a similar highly expressed receptor to interact with DC.
The publications and other materials used herein to illuminate the background of the invention, and in particular, cases to provide additional details respecting the practice, are incorporated herein by reference and, for convenience, are referenced by author and date in the text and respectively grouped in the appended List of References.